Avoid direct sunlight, heat, or draughts which can shorten flowers' lives
Top up the water regularly .Use cold water .
Put the flowers in a fresh and ventilated place
Cut stems at an angle.This gives the stem a bigger area to take up more water, and stops it resting on the bottom of the vase and sealing itself.
Use lukewarm water - there's less oxygen in it, and helps prevent air bubbles in the stem that will block water uptake. It also encourages some flowers to open up.